Anionic surface active agents, such as alkyl benzenesulfonates, higher alcohol sulfates, alkyl ether sulfates, and higher fatty acid salts, have widely been used in detergents, such as shampoo. The detergents containing these surface active agents are unsatisfactory in mildness to the skin. On the other hand, there is now a tendency that an N-acylglutamic acid salt obtained by subjecting one of amino acids, glutamic acid to acylation is incorporated into hair shampoo or body shampoo not only because of its mildness to the skin but because of its inhibitory effect on growth of harmful microorganisms causing skin diseases.
However, an aqueous solution of the N-acylglutamate per se lacks detergency and foamability for cleaning off extremely oily dirt, for example, hair applied with pomade.
It has been proposed to use the N-acylglutamate in combination with an alkyl betaine or imidazoline surface active agent to thereby improve detergency and foamability without impairing mildness to the skin as disclosed in JP-B-50-23682 and JP-B-51-42603 (the term "JP-B" as used herein means an "examined Japanese patent publication"), but these detergents are still unsatisfactory in detergency and foamability.